Fluid motor



May 18, 1943 M. KRAUT FLUID MOTOR Filed Nov. '7, 1941 2 Sheets-Sheet 1INVENTOK,

ATTORNEY.

db o/acemeaf May 18, 1943 M. KRAUT FLUID MOTOR Filed Nov. 7, 1941 2Sheets-Sheet 2 INVENTOR, Max MW 7,

ATTORNEY.

Published May 18, 1943 FLUID MOTOR Max Kraut, La Libertad, Chontales,Nicaragua,

assignor .to Southwestem Engineering Company, Los Angeles, Calif., acorporation of California Application November 7, 1941 Serial No.413,156

13Claims.(Cl.121-1G4) W This invention relates broadly to fluid motorsand more particularly to a fluid driven apparatus for producingreciprocation of a. member normally'subject to a force acting in onedirection. Such motors are particularly'useful in operating jigs for therecovery of minerals, such for examv ple as the improved jigs shown inmy co-pending applications Serial No. 228,518, filedSeptember 6, 1938,now Patent No. 2,271,650, issued February 3, 1942, and Serial No.319,613, filed February '19, 1940, of which this present application isa continuationin part. As disclosed in said co-pending app1ications, ajig is broadly an apparatus comprisinga permeable bed, preferablycomposed of sand and other 7 particles, supported by, a screen, overwhich flows a mixture ofwater, gangue, and the mineral desired to berecovered, there beingmeans to provide an intermittent upward now ofwater through thebed, resulting in a classifying, action therein bywhich the relatively heavy mineral de- The major object of my inventionis to provide simple and efliciemt actuating means which-is capable ofimparting a rapid reciprocating motion to a jig or other device desiredto be reciprocated, which motion is of suchnature that. the

velocities during upward and downwardstrokes [may be kept approximatelyconstant over ap-' proximately the entire strokes, and the velocityduring the downward stroke can be much greater than the velocity duringthe upward stroke. 1

Another object of my invention is toprovide' become apparent from thefollowingdescription of different embodiments of'my invention and fromthe accompanying drawings in which:

Fig. 1 is'an elevational view, partly in section,

showing one embodiment of my invention, the

controlling valve member being shown in the sition in which it isundeflected,

Fig. 2 is a horizontal sectional view of the apparatus of Fig. L'tak'enalong the line 2-2, V

Fig- 3 is a diagrammatic view showing the controlling valve in itsuppermost position,

' Fig. 4 is a view similar'to Fig. 3. but showing the valve in itslowermost position.

Fig. 5. is a-vertical sectional view of a. modified form-of fluid motorembodying my invention, the controlling valve member being shown in theposition in which it. is undeflected,

Fig. 6 is an enlarged sectional view of the bellows forming a part'ofthe motor shown in Fig. 5, Fig. 7 is a partial sectional view of thefluid motor of Fig. '5, showing the controlling valve in its lowermostposition,

Fig. 8 is a view similar to Fig. 7, but with the valve in its uppermostposition, and g Fig. 9 is a diagram illustrating the manner of variationof displacement of the moving parts of my fluid motors with time.

Referring now, to the drawings, and particularly to Figs. 1-4 thereof,the numeral I0 designates a vertical shaft or rod adapted to be attachedto the body to be reciprocated, in the case of a jig, this being thecollecting .pan. Under normal conditions,=the rodlfl willtendto movedownwardlyin response to the gravitational pull thereon. The rod I0 ismovably mounted, and is adapted to be reciprocated in 'a vertical pathas will nowbe described. a

An outer cylindrical housing II is secured to a bridge-like structure 12adapted to span a jig or otherapparatus'fromside to side in convenientmanner. Within the housing H is locateda cylinder l3 attached to thehousing II at circum- 'ferentially spaced locations and opening at topand bottom into the housing I I. A water supply pipe 34 is screwedintothe housing II and cylinder I3 and feeds water under pressurevdirectly into thecylinder' 13. The cylinder 13 at its lower end isconical in shape and serves as a valve seat l4 for a circular valve disc15 of resilient ma terial, such for example a rubber,j.which ipreferably of tapering cross-section, facilitating flexing of the disc.,4 piston 16 closely fitting the cylinder I3 is adapted to move-thereinabove the water inlet pipe, 34. The piston l6 and valve memberliaremounted on an axial tube ll,

- being pressed against the shoulder It by the tighteninglof nut l9, Thevalve disc 15 has'an area less than that of the piston; l6 and i mountedso asto be unsupported in its peripheral portion. The tube ll extendsupwardly through a bearing 20 mounted in .acover 2| secured to the topof housing H by bolts 22. A lubricating fitting 23 is connected throughthe cover 2| to conduct lubricant to the bearing 20.

A diaphragm 2|, preferably of rubber or can vas, and apertured to permittube H to pass therethrough, is clamped between housing I i and cover 2|to protect the bearing 20 from splash of water. The rod ll! passesthrough the tube IT, has a shoulder abutting the lower end of tube II,and carries a nut 25 in threaded engagement therewith at its upper endwhich securely clamps the tube I1 and associated parts on the rod N formovement therewith. A spring 26 surrounds the tube l1, bears-at one endonpthe cover 2| and at the other end against a. washer 21 retained in anadjustable position by nut 28 in threaded engagement with tube II. Thespring 26 acts to balance part of the load on rod ill due to the weightof the rod I and its associated parts, whereby the pressure and amountof fluid required to operate the reciprocating means is re- 7 duced. Itshould be noted that the spring 26' should never be made sov strong asto completely balance all the load on rod 10, for then auxiliary meanswould have to be supplied to return the valve to the closed position.Attached to the housing II at its lower end and in communication with.the' space within, the

' housing II and cylinder [3 is a fitting 29 having a side outletpipe'30 connected thereto and a pipe 3! connected to the bottom,surrounding rod l0, there being space left between the rod lliand pipe3l.- The pipe 3| may pass downwardly through the piston II to be pulledrapidly downward by the weight of rod l0 and its associated parts. Assoon as the piston and valve structure has.

fallen to a point where disc contacts seat i4, pressure starts tobuildup again in cylinder I3. Since, however, the disc I5 isflexible,'it can be distorted into the shape shown in Fig. 4 in whichcondition the volume within the cylinder between piston l6 and valvedisc i5 is greater than in the condition illustrated in Fig. 1. It willbe obvious that pressure cannot build up to a normal value within thecylinder so long as this volume is increasing. For this reason, thepiston l6 and valve disc l5 sink to a lowermost posiiton illustrated inFig. 4. The pressure within the cylinder then builds up quickly andcauses the piston I6 the bed of the jig and into the hutch, if the motorisbeing used to operate a, jig.

In the bottom of fitting 29 is preferably located a washer 32,preferably of rubber, clampedbetween a shoulder of the fitting and a nut33 in threaded engagement with the fitting. The washer 32 may pack therod lll'in contact therewith to prevent passage of any fiuid'into thepipe to be raised while the periphery of the disc I5 is held in contactwith seat ll, the piston and disc going through the position shown inFig. 1 and on through the remainder of the cycle as previouslydescribed. Since any momentum possessed by the moving parts at the timeof unseating of the valve disc I; is quickly overcome by the unbalancedforce of gravity, there is very little upward movement after this time,and nearly all of the upward stroke of the member I! takes place whilethe valve disc 15 is seated on the seat l4.

The water discharged from the cylinder past the disc l5 when in the openposition passes'into the fitting 29 andout through pipe 30, a portionThe diaphragm shield 2| prevents any of this water from splashingup-into the bearing 20.

3| or it may be of'any suitable internal diameter to permit'passage ofany desired proportion of the available fluid past the washer, pipe IIand into the hutch.

In the. operation-of this form of my actuating means'to reciprocatetherod l0, liquid, preferably water; .under pressure enters cylinder 23through pipe 34 and acts upon both piston l8 and disc ll,'the force onpiston IS in an upward direction being greater than the downwardlydirected force on 'the valve member 15 by reason of the greater area ofpistonl8. The piston 18 therefore moves upwardly; If the disc [5 wereinfiexibleit would also move upwardly coincidentally with piston I 6;but being flexible, the

periphery of disc I 5 is held down in contact with the conical seat Iwhile the center of the disc connected to piston l6 rises with thepiston, as

through the shown in Fig. 3. The piston it continues to rise y until a.critical point is reached where the pein contact with the seat H by thewater pressure, and the disc 15 then breaks from the seat.- The valvedisc snaps open quickly as the pressure on opposite sides of it quicklyequalizes. At the same time the piston it moves farther up in the cyl-'inder due to the momentum it has acquired. Thus the opening closed bydisci is rapidly opened, resulting in an instantane'ous'drop inpressure; which, among other things, depends ing between the seat lland-the disc 15 causes 75 strokes. It-is to be riphery of the disc I5can no longer be'held The resulting reciprocation of rod [0 is veryrapid and regular. The'number of strokes perminute may be adjusted byvarying the diameter of the disc I! or by varying the restriction of thewater supply. In one embodiment of this form of my device, about 200complete cycles per minutewere obtainable with a disc 5 inches indiameter,-and with a disc- 4' inches in diameter thenumb'er of cyclescould be adjusted from 400 to 1000 per minute, finally reaching avibratory movement. 'The extent of the movement depends'uponthe diameterof the disc l5, greater movement being obtained, within limits, by useof a disc of a larger diameter. In the device above referred to,amovement of 1 inches was obtained by use of a'disc 5 inches indiameter, while a movement of /4 inch was obtained by use of a disc of 4inches in diameter.

The movement of the piston I 6 is relatively I slow on its upward strokebecause a relatively large weight is being lifted by the water pressureacting only onthe differential, area of piston l6 and disc ill, while onthe downward stroke the weight connected with rod Ill pulls the pistondown veryrzp'idly against a greatly reduced pressure. upward anddownward velocities of the member l8 and associated parts areapproximately constant over. approximately the entire stroke thereof.This type of reciprocation involving a rapid downward stroke of constantvelocity and' a relatively'slow upward stroke of constant vev locity hasbeen found to be particularly well 1 adapted to operation of a jig,resulting in more emcient. recovery than with reciprocation of equalvelocity on. the two oppositely directed understood, of course, that Itis found by actual test that both the Y the reciprocating means herein.disclosed may 54 is connected a fltting 28 having a side disbeadvantageously employed in jigs of'various constructions and may also beused for purposes other than reciprocation of a jig. Referring now toFigs. to 8, wherein is illustrated a modified form of fluid motoractuating means embodying my inventiomthe numeral II again indicates ahousing which may be secured to a bridge-like structure l2 spanning-ajig from side to side or. attached to other means to beoperated. Thehousing II is at its lower end preferably conical in shape and serves asa valve seat H for a resilient valve disc 48, preferably of rubber,which is connected for movement with.

the rod ID. The valve disc 48 may be clamped between a shoulder on thesleeve member I .and a nut l9, and the sleeve member |'|.may be heldagainst a shoulder on the rod IO' by means of a sleeve member 52 on therod I0 and a nut 25 threadedon the upper end of therod Ill.

The valve member 48 in this form of my in-. vention is preferably oftapered cross-section, being thin nearthe center support to provideflexibility, and thickest at theperipheral edge to prevent the valvemember from passing through the outlet .54 from the housing. I find thatwhen I use a valve member 48 having a thick edge, asshown, it ispossible to considerably increase the size of the outlet 54 over thatwhich is possible when using a relatively thin-edged valve member suchas-that previously described herein, and still keep the valve memberfrom passing through the outlet on the 1 downward stroke. It will beevident why thisis so from an inspection of Fig. '7 in which the valvememher is shown in its lowermost position. It will be observed that inthis position the lower peripheral edge of the valve member is. forcedeven farther out radially than when the valve member is undeflected.Thus, a tendency of the valve member to pass. through the outlet 54 onthe downward stroke is averted;

A bellows55 of. flexible material, preferably rubber, and ofdiameter-larger than the valve member 48, is housed within the housingI, having its upper end .clamped between the housing H and a cover 2|and its lower end attached to a plate 51 clamped between the sleeves l1and 52. The bottom of the bellows thus constitutes a movable wall of thefluid chamber, similar in effect to the movable wall piston l6 ofFig. 1. Within each of the outwardly extending folds of the bellows 55,for lateral reinforcement of the bellows, I preferably place a metalring 58, and fall of the rings 58 are preferably held in place by meansof a plurality of strips 68 offlexible material, preferably'rubber whichare vulcanized or otherwise secured to the insidesurface of the bellowsso as .to cover over the rings 58 at locations circumferentially spacedaround the bellows. A hole 6| is located in the cover 2| to permit airto freely move into and out ofthe space within the bellows 55.

The sleeve'52 is slidably guidedin a bearing in the cover 2|, and acompression spring 26 surrounds the sleeve 52 and at one end abuts thecover 2| and at the other end abuts a nut 28' threaded on the sleeve 52.The spring 26 acts to balance part of the load dueto the weight of theparts supported by rod l0.

A water inlet pipe 34, provided with a control valve not shown,discharges into the chamber formed within the housing H at a pointbetween the valve member 48 and'the bellows 55. To

the outlet end'of the housing I below the outlet charge pipe 30connected thereto and a pipe 8| connected tothe bottom thereof andsurrounding the rod l0. Space is left within the pipe 3| around the rodI0 for-the passage of water. The pipe 3| may pass downwardly throughthebed of a jig'and open into the hutch thereof when my device is beingused in connection therewith. In

' tion of the motor.

the bottom of the fitting 28 is located a washer 32, preferably ofrubber, clampedbetween a shoulderof the fitting and a ,nut 33 inthreaded engagement with the fitting. The :washer 32 may pack the rod IDin contact'therewith to prevent passage of any fluid into the pipe 3|orit may beof any suitable internal diameter to permit-passage of anydesired proportion of the available water past the washer, and throughthe pipe 3|.

I have found that water which is passed through the motor generallycontains air which is to some extent released within the housing l andaccumulates in the uppermost portion of the so as to continuously pass asmall stream of water which effectively sweeps airwout of the fluidchamber of the motor and preventsits accumulation therein.

'In the operation of this form of my fluid motor to'reciprocate the-rodID, a fi'uid,'preferably water, underpressure enters through the pipe 34and acts upon both the-valve member 48 and the movable wall comprisingthe plate 51' and the 1 under side of the bellows 55, the force on thelatter being'greater than that on the valve member 48 by reason of thegreater area acted upon.

The rod- I0, is, therefore, moved upwardly. Since the valve member 48 isflexible, the periphery thereof continues to be held down against itsseat by water pressure while the rod 10' moves upwardly. The rod Illcontinues to move upwardly until the valve member '48 is deflected 'tosuch an extent that the water. pressure on it can no longer hold itsperiphery on the seat; M.

The conditions existing at this moment may be as illustrated in Fig. 8.Following a slight additional upward movement of the rod III, theperiphery of the valve member 48 will, snap up:

- instantaneous drop of the pressure beneath the wardly by reason ofits'resi'lience and open a passageto the outlet 54. Water then immedi'-ately' rushes out of the outlet 54 and there is an bellows 55. The'heavyweight of the rodl0 and its associated parts oauses'the rod' I8 to droprapidly. When it has fallen to a point where the valve'member 48contacts'the seat I4, pres-- sure starts to buildup again in the fluidchamher, but because of the momentum of the-moving parts, they fall toa'point where the. conditions may be as illustrated'in Fig. '7.

movement and starts to move the bellows 55 and rod l0 upwardfthe motoragain going through the cycle described above. The reciprocation of Atthis "point fluid pressure has overcome the downward the rod Ill may bemade slow or rapid as desired by control of the'valve on pipe 34.,

It is important to note that in the action of the fluid motors of myinvention, any substantial movement of the movable wall comprising thepiston ll; of Fig. 1 or the plate 51 and the bottom of the bellows ofFig. 5 results in a corresponding movement of the rod l0, and that thevalve member I5 or 48, as the case may be, is sufficiently flexible sothat while the valve member is still closing the outlet the rod in ispermitted to move through nearly its full stroke in the upwarddirection.

The water which is discharged from the motor passes into the fitting 29and out through the pipe 30, a portion thereof, depending upon theopening between the washer 32 and the rod l0, passing down the pipe 3|to supply make-*up water to the hutch.

The type of reciprocation resulting from the operation of the motorsherein described .is di,-

agrammatlcally illustrated in Fig. 9 and is characterizedby relativelyslow upward strokes AB, CD, EF, etc., during which the displacementvaries sub-stantialy uniformly with time, and relatively rapid downwardstrokes BC, DE, FG, etc., during which the displacement variessubstantially uniformly with time. Thus, both the upward and downwardvelocities of the rod l0 and the water in the hutch of the jig areapproximately constant over approximately the entire stroke, while thedownward velocity is much greater than the upward velocity. Theimportance and value of these velocity conditions is evident from thefollowing analysis. I

In order to'maintain the permeable bed of a jig in a state orsuspensi'onand to secure the greatest amount of work from the jig per unit of time,it is desirable to move the water upwardly and downwardly through thebed with a relatively large number of alternations of movement per unitof time. But topermit high recovery of fine concentrate particlesfit isdesirable to employ not, too great an upward velocity of water. The mosteflicient condition, therefore, is one in which the downward velocity ofwater is considerably greater than the upward velocity of the water, forby this means the upward velocity may be limited to an eflicient valueand the number of strokes per unit oftime may be maintained large-If,vhowe'ver,' the downward velocity is too great at any time, the bedtends to pack too severely, so it is clear that with a given maximumamount of water desired to be moved downwardly and a definite limitplaced upon the maximum instantaneous downward velocity, the mostefficient condition will be that in which the downward velocity isapproximately constant over approximately the entire period of downwardmovement. By this means a sumciently rapid alternation of movement issecured to maintain the bed in an efllcient condition and it isprevented from packing severely on the downward stroke. It will also beevident that the most efllcient condition during the upward stroke isone in which the velocity is approximately constant over approximatelythe entire stroke because for any other condition during these periodswhen the velocity is higher than the most suitable velocity, properrecovery of fine concentrate particles is being hampered, while duringthose periods when the velocity is less than the permissible value, timeis simply being wasted and could better be employed in increasing thenumber of alternations per unit of time.

From the foregoing it will be seen that both of the embodiments of myinvention herein described are capable of attaining the objectsandaccomplishing the advantages hereinbefore set forth, and it is to beunderstood that I do not mean to be limited to any of the specificshowings herein except as limited by the claims appended hereto.

I clalm as my invention:

1. Apparatus for producing reciprocation of a member normally subject toa force acting in one direction, which includes: a cylinder having anoutlet at one end; a piston movable in said cylinder and connected tosaid member in such manner that movement of said piston results in acorresponding movement of said member; a flexible valve disc of arealess than that of said piston and connected to said member, said valvedisc being adapted to close said outlet upon movement in response tosaid normally acting force and being sufliciently flexible to permitmaterial movement of said" member while still closing said outlet; andfluid supply means connected with the interior of said cylinder betweensaid piston and said valve disc.

2. ,;Apparatus for producing vertical reciprocation of a member urgeddownwardly by the force of gravity on ;said member and its associatedparts, which includes: a spring acting to partially balance said forceof gravity; a cylinder having an outlet at the lower end; a pistonmovable in said cylinder and connected to said memher in such a mannerthat any substantial movement of said piston results in a correspondingmovement of said member; a flexible valve disc of area less than thatvof said piston and connectedto said member, said valve disc beingadapted to close said outlet upon downward movement. and beingsufficiently flexible to permit 'material movement of said member whilestill closing said outlet; and fluid supply means connected with theinterior or said cylinder between said piston and said valve disc.

, 3. Apparatus for producing reciprocation of a member normally 's jectto a force acting in one direction, which includes: a cylinder having anopening at one end and a conical surface adjacent said opening; a,piston movable in said cylinder and connected to, said member in such-manner that movement of said piston results in corresponding movementof said member; a flexible valve disc of area less than that or saidpiston and connected at its center to said member, said valve disc beingadapted to engage said conical'suriace to close said opening uponmovement in response to said normally acting iorce and beingsufficiently flexible to permit material movement of said member whilestillclosing said outlet; and means for supply- .ing fluid underpressure to the interior of said a piston movablein saidcylinder andconnected to said member in such manner that movement of said pistonresults in movement of said member; a flexible valve disc of area lessthan that of said piston and'connected at its center to said member,said valve disc being adapted to engage said conicalsurface to closesaid opening upon downward movement; and means for supplying fluid underpressure to the interior of said cylinder between said piston and saidvalve disc.

5. Apparatus for producing vertical reciprocation of a member urgeddownwardly by the force of gravity on saidmemberand its. associatedparts, which includes: a housing open at its lower end; [a cylindercontained within said close said opening upon downward movement andbeing sufflciently flexible to permit material movement ofsaid'memberwhile still closing said outlet; means for supplying fluid tothe interior of said cylinder betwee'nsaid piston and said valve disc; acover attachedto the top of said housing through which saidmemberfiextends; a' bearing in said cover serving as a guide for saidmember; and a shield clamped between said housing and said coverpositioned between the top of said cylinder and said bearing andapertured to permit said member to pass therethrough.

6. Reciprocating, apparatus, which includes: walls forming a chamberprovided with an inlet and an outlet for fluid, one of the walls of saidchamber being movable; a reciprocable I member connected to said movablewall in such manner that any substantial movement of said movable wallresults in corresponding movement of said member; a valve element ofarea less than that of said movable wall and associated with saidreciprocable member to normally close said outlet, said valve elementbeing adapted to continue to close said outlet during initial movementof said reciprocable member in a direction corresponding to outwardmovement of said member normally subject to a'force acting in onedirection, which includes: walls forming, a cham her having a fluidinletand'a fluid outlet, one of said walls being a movable wallpositively connected to said member in such manner that an increase inthe volume of fluid in said chamber causes a proportional movement ofsaid memher; and a flexible valve disc of area less than that of saidmovable wall connected to said member, said flexible'valve disc beingadapted to close said fluid outlet upon movement of said member inresponse to said normally acting force and having an unrestrained areacapable of'distortion to maintain said fluid outlet closed throughoutsubstantially the entire stroke of said member caused by increase in thevolume of fluid in said chamber; I

9. Apparatus for producingreciprocation of a member normally subject toa force acting in one direction, which includes: a cylinder having anopening at one end and a conical surface adjacent said opening; a pistonmovable in said cylinder and positively connected to said member in suchmanner that an increase in the volume of fluid in said cylinder causes aproportional movement of said member; a flexible valve disc of area lessthan that of said piston and connected at its center to said member,said valve disc being adapted to engage said conical'surface to closesaid opening upon movement in response to said normally acting force andhaving an unrestrained area capable of distortion to maintain saidfluid. outlet closed throughout substantially the entire stroke of saidmember caused by increase in the volume of fluid in saidcylinder;

'and walls forming a passage for inlet of. fluid into the interior ofsaid cylinder between said piston and said valve disc.

10. Apparatus for producing vertical reciprocation of, a member urgeddownwardly bythe force of gravity on said member and its associatedparts, which includes: a spring compressed between said member and astationary part 01' said apparatus acting to partially balance saidforce of gravity; means for adjusting the force exerted by said spring;a stationary housing; a cylinder contained within said housing andsupported thereby at circumferentially spaced locations,

said cylinder having an opening at its lower end movable wall but to beunseated by continued movement of said reciprocable member to open saidoutlet.- v

7. Apparatus for producing reciprocation of a member normally subjectto. a force acting in one direction, which includes: walls formingachamber provided with an inlet and anoutlet for fluid, one of the wallsof said chamber being movable and connected to said member in suchmanner that any substantial movement of said movable wall results incorresponding movement of said member, and a flexible valve disc of areav 8. Apparatus for producing reciprocation of a and a conical surfaceadjacent said opening; a piston movable in said cylinder and positivelyconnected to said member in such manner that an increase in the volumeof fluid in said cylinder causes a proportional movement of said member;a flexible valve disc of area less than that of said piston andconnected at its center to said-memher, said valve disc being adapted toengage said conical surface to close saidopening upon-downward movementand having an unrestrained area capable of distortion to maintain saidfluid "outlet closed throughout substantially the entire stroke of saidmember caused by increase in the volume of fluid in said cylinder; andmeans for supplying fluid under pressure to the interior of saidcylinder between said piston and said valve disc.

11. In a water-driven reciprocating means the combination of: a housingproviding a water chamber within, a waterinlet to said chamber on theside of said housing, and a water outlet at the bottom of said housing;a bellows secured at the top of said housingand extending into saidchamber; a reciprocable member attached to the bottom of said bellows; aresilient valve'member connected with said reciprocable member and thebottom of said housing; a bellows secured at the top of said housing andextending into said chamber; a reciprocable member attached to thebottom of said bellows; a resilient valve member connected with saidreciprocable member and adapted to close said outlet upon downwardmovement of said reciprocable member, said valve member being of arealess than that of the bottom of said bellows; a conduit in communicationwith said chamber adjacent the highest point thereof and extending in anupward direction from said chamber; and a control valve in said conduitlocated at an elevation higher than any point of said chamber.

13. In a fluid-driven reciprocating means including walls forming achamber provided with an inlet and an outlet for fluid, one'of the wallsof said chamber being movable, and a reciprocable member connected tosaid movable wall in such manner that any substantialmovement of saidmovable wall results in corresponding movement of said member; a valvedisc of resilient material of area less thanthat of said movable walland connected to said member, said valve disc being adapted to closesaid outlet upon downward movement and being of tapered crosssectionwith the thickest unsupported portion of said valve disc being locatedat the periphery thereof. .e

MAX KRAUT.

